[NTG-context] problem since previous versions

7 Jun 2020

      A problem has arisen up since previous versions, where code without a problem now raises an error.

This is the afflicted code:
	% Assign values to \locationbox.
	\doif{top}{\placexlocation}%
		{\def\startlocationbox{\vtop\bgroup\vss}}%
	\doif{center}{\placexlocation}%
		{\def\startlocationbox{\vcenter\bgroup}}%
	\doif{bottom}{\placexlocation}%
		{\def\startlocationbox{\vbox\bgroup}}%

And it is used here:
	\setbox\placexbox=\startlocationbox
		\ignorespaces

Previously this worked without a hitch, now the error is:
tex error       > tex error on line 9 in file ./familie-events.tex: ! A <box> was supposed to be here
<to be read again> 
\vcenter 
\startlocationbox ->\vcenter 
                             \bgroup 
\dostartcontentplacexinline ...ables \par \setbox \placexbox =\startlocationbox 
                                                                                \ignorespaces 
<to be read again> \syst_helpers_single_empty_one_nop 
                                   \xmlflush 
\21>:xmlplc:placexcontent ...le=\xmlatt {#1}{alttitle}]}\startcontent \xmlflush 
                                                                                {#1}\stopcontent 
l.9 }

I can try to make a minimal example, but not without the afflicted module of some 800 lines. So perhaps the problem will be located by the experts at first sight. It is of course the \vcenter playing havoc, because replacing it by \vtop or \vbox makes the error disappear.

Thanks for looking into it, because my work more or less depends on this code working in good order.

dr. Hans van der Meer